The overall goal of this proposal is to elucidate the structural mechanisms which give rise to the unusual kinetic characteristics of the mitochondrial form of human aldehyde dehydrogenase (ALDH2). This is tied to the long-range goals of our IRPG group by providing a structural context for the understanding of functional information obtained through the studies in Dr. Henry Weiner's laboratory. Human ALDH2 catalyzes the NAD-dependent oxidation of aldehydes to their corresponding acids. Decreased ALDH2 activity, resulting from inhibition by ANTABUSE or as a result of a common polymorphism in the Asian population (ALDH2x2; E487K), is associated with an aversive reaction following alcohol consumption and hence a lower incidence of alcoholism and alcohol abuse. The overall hypothesis of both components in the IRPG group is that only a complete understanding of both the functional and structural properties of this important enzyme will permit the design of new alcohol aversive agents which show greater selectivity than those currently available. We plan to achieve these goals by determining the three-dimensional structure of human ALDH-2 in complexes with various inhibitors and activators. The information obtained from these experiments will provide a detailed structural picture of the enzymatic intermediates which arise during catalysis and will ultimately permit the targeting of different catalytic steps by specific inhibitory agents. We will also determine the structural basis for the dominant inactivation of ALDH2 produced by the mutation of Glu487 to Lys which is found in approximately 50 percent of the Asian population. These studies will examine the mechanism by which structural perturbations in one subunit can be communicated to other subunits in the tetramer and may lead to the development of novel inhibitory agents which act in an allosteric manner.